The protein 5-lipoxygenase (5-LO) is associated with the pathway of leukotriene synthesis. Upon presentation of inflammatory stimuli from the exterior of the cell, calcium is released and binds to phospholipase A2 (PLA2) and 5-lipoxygenase. Cell activation results in the translocation of PLA2 and 5-lipoxygenase from the cytoplasm to the endoplasmic reticulum and/or nuclear membranes, where in the presence of 5-lipoxygenase-activating protein (FLAP), 5-lipoxygenase can then catalyze the two-step oxygenation and dehydration of arachidonic acid, converting it into the intermediate compound 5-HPETE (5-hydroperoxyeicosatetraenoic acid), and in the presence of FLAP convert the 5-HPETE to Leukotriene A4 (LTA4).
Leukotrienes are biological compounds formed from arachidonic acid in the leukotriene synthesis pathway (Samuelsson et al., Science, 220, 568-575, 1983; Cooper, The Cell, A Molecular Approach, 2nd Ed. Sinauer Associates, Inc., Sunderland (MA), 2000). They are synthesized primarily by eosinophils, neutrophils, mast cells, basophils, dendritic cells, macrophages and monocytes. Leukotrienes have been implicated in biological actions including, by way of example only, smooth muscle contraction, leukocyte activation, cytokine secretion, mucous secretion, and vascular function.